Adenosine triphosphate (ATP) is a complex fundamental energy currency for all life by transferring energy from chemical bonds to energy absorbing reactions in the cell. This multifunctional nucleotide, consists of a nucleoside adenosine along with three linked phosphates.

ATP more specifically has the role of converting low-energy covalent bonds from the nutrients we eat into high-energy bonds in order for most biological reactions to occur. The low energy bonds are not very useful for biological processes, whereas the high energy bonds that release energy when ATP goes to ADP are just right to run biological mechanisms. In the cell, ATP, or a similar molecule (GTP, guanosine triphosphate) supplies energy whenever one of its three phosphates are cleaved during a reaction known as "hydrolysis". [1] All known organisms use ATP to power their cells, which avoids each cell needing a special food supply for every different activity.

The supply of ATP must be steady because its lack would kill an organism in a matter of minutes. Poisons like cyanide kill so quickly by blocking processing of ATP according to Bergman [2] Bergman cites references that one billion ATP molecules in each cell are each recharged about three times a minute to maintain cell activity. He notes that a human body contains only about 50 grams of ATP, but if it were not continually recharged we would need 400 pounds of ATP to maintain activity for one day at the rate of 2,500 calories per 24 hours.

The cell manufactures ATP from glucose by a process known as glycolysis.[1] ATP can be important as an indicator of cell health. The Fraunhofer Research Institution for Modular Solid State Technologies (EMFT) in Munich, Germany, has developed nanoparticles that carry fluorescent dyes that react when ATP is present. Nanoparticles can cross cell membranes easily, and when the cells are examined by a fluorescence microscope, the nanoparticles indicate the presence of ATP. For example, if cancer cells are being tested, those that are damaged by a certain chemical will only show the red base dye, while healthy cells glow green or yellow because they are producing much more ATP.[3]